A fundamental study on indium electrochemistry in molten NaCl-KCl eutectic: toward new technology development for indium secondary resources recycling

In this work, a fundamental study on the electrochemical behavior of indium on a molybdenum electrode in the molten NaCl-KCl eutectic system at 750 °C was carried out. A variety of transient electrochemical techniques such as cyclic voltammetry, chronopotentiometry, square wave voltammetry, and linear sweep voltammetry were utilized to clarify the redox mechanism of indium in the molten melt. The results showed that the reduction of In(III) to metallic In is a diffusion-controlled one-step process of reversibility. The diffusion coefficient of In(III) in the eutectic NaCl-KCl system at 750 °C was evaluated by cyclic voltammetry and chronopotentiometry, and the results obtained by the two electrochemical methods accord well with each other, as to be approximately 1.05×10−5 and 3.7×10−5 cm2/s, respectively. This study aims to provide a theoretical basis for the development of an efficient and cost-effective process for indium secondary resources recycling on the basis of molten salt electrochemistry.